Four-way valves of the spool type have been, and still are, extensively utilized. In this spool-type valve, a control spool is slidably supported within a housing, and a plurality of elastomeric O-rings coact between the spool and the housing for creating a slidable but sealed engagement therebetween. Even though extensively utilized, these spool-type four-way valves have possessed operational features which have long been recognized as undesirable. For example, the presence of the elastomeric O-rings for creating a slidable seal between the spool and housing imposes a substantial frictional drag which impedes free shifting of the spool, and also causes substantial wear of the O-rings due to the continual sliding therealong.
Because of the friction and wear problems associated with spool-type four-way valves, attempt have been made to provide a satisfactory four-way elastomeric poppet valve, although to the best of my knowledge no one has previously succeeded in designing a four-way elastomeric poppet valve having characteristics which would be considered more closely approaching optimum performance.
For example, with a four-way poppet valve, the valve is again provided with shiftable valve stems or spools, but in this case the valve stem mounts an enlarged elastomeric rigid valve seat (i.e., a poppet) which moves into and out of engagement with rigid valve seats formed on the housing. This thus minimizes wear of the poppet, and also greatly reduces friction during the shifting or sliding of the valve stem. However, while prior four-way poppet rigid valves have minimized or overcome the wear and friction problems associated with spool-type valves, nevertheless the known poppet valves have created additional undesired characteristics.
For example, most of the known four-way poppet valves have required a substantial number of valve stems so that the overall valve assembly is structurally and mechanically complex. For example, U.S. Pat. No. 3,963,048, as owned by the assignee of this application, discloses a four-way poppet valve which requires four separate valve stems each having a poppet thereon to achieve a four-way valving function.
Another, and more significant, problem associated with four-way poppet valves is that such valves have normally required one or more poppets to seal against the fluid pressure. That is, when the poppet is seated against its valve seat so as to be in a closed position, the fluid pressure acts against the poppet in a direction tending to push the poppet away from its closed or seated condition. This hence increases the difficulty of obtaining a desirable sealed relationship when the poppet is closed. For example, it has been observed that as the pressure of the fluid is increased, it is necessary to increase the hardness of the elastomeric poppet to prevent leakage when sealing against pressure, and this in itself creates an undesirable condition because the harder material of the poppet usually will not seal as well under operating conditions involving low fluid pressures. Likewise, as the fluid pressure increases, the valve requires a proportionally greater force to hold the poppet against the valve seat, and this is also an undesirable condition.
Accordingly, it is an object of this invention to provide an improved four-way poppet valve which overcomes the above-mentioned disadvantages.
More specifically, it is an object of the present invention to provide a four-way poppet valve which utilizes only two shiftable valve stems.
A further object of the invention is to provide a four-way poppet valve, as aforesaid, wherein the poppets seal with, or in the direction of, the net pressure exerted by the pressurized gas, such that the pressure acts to press the poppet onto rather than push it off of the seat.
It is a further object of the invention to provide a valve, as aforesaid, that provides longer poppet life and reduced operating energy consumption due to the substantial balance of pressures on the poppets.
The present invention relates to a four-way poppet valve having a housing provided with a pair of parallel bores, and a pair of valve stems slidably supported within the bores, each valve stem having one or more elastomeric poppets thereon for controlling fluid flow. A supply port communicates with one of the bores, whereby flow therethrough is controlled by the respective shiftable valve stem through intermediate passages to the second bore, which second bore communicates with both the exhaust port and a pair of load ports. The shiftable valve stem in the second bore respectively controls flow between the ports which communicate therewith. The bores, and the valve stems associated therewith, define various chambers which cooperate with the poppets on the respective valve stems for confining therein fluid pressure so that the valve poppets, when in a closed or seated condition, are always urged in the seated direction by the fluid pressure.